I'm just wondering what the heck the VSS signal coming from the NVG 149 transfer case is used for?

The transfer case itself doesn't use any input from the PCM to work correctly right? It's basically a "dumb" mechanical case that is AWD full time AFAIK.

I wonder if it's used for the traction control system on some vehicles?

Just trying to find some answers because that is one of the hurdles to swapping a 4L80E into an AWD vehicle. I'm not swapping now but, if the 65e ever goes I will not put another back in.

 

the VSS is there simply to check output speed of the rear shaft. from this the computer decides vehicle speed, shift points, rev limiter, etc. i don't think there is a sensor for the front shaft. the viscous coupler is purely mechanical. as far as i know, there is only one AWD SS with a 4L80E that i know of.

 

Yeah, Kurt at W2W has a 4L80E in his. Not sure what he had to do to the computer to get it working.

I wonder what the problem is with putting a 4L80E in then. Couldn't the sensor wire from the transfercase just be used for the rear VSS signal output from a 4L80E transmission? I wonder if the signal from the transfercase is the same as what the signal from the transmission looks like. Maybe that is the problem.

 

well figure it out and let us know

 

 

well I know from comparing the vss on my 2003 2wd to white1's older 4wd that my vss is on the tailshaft of the transmission, his is mounted on top of the transfer case (which of course replaces the tailshaft section when compared to a 2wd). That is the only vss on his 4wd truck, is this the one you are referring to?

I hope this information clears it up a bit.

 

You know, I was under the truck today changing the oil and didn't pay any attention if there was only one VSS wire under there. The one on the transfercase is the one I'm talking about.

I'm gonna take another look tomorrow.

 

when i went to the 80, i noticed the 60 only had one sensor and the 80 had 2. The pcm wants to know input and output. just like zippy points out, the Tcae is the output (1:1) and the front sensor on the 80 will be the input.

I am a little foggy on the swap, it's been quiet a few months and I didn't keep good records, but I belive that's how it went.

You get it wrong on the 80 swap and you'll know instantly, the pcm will tell the trans to shift when it's in 4th already....ie;surging.

MY swap was in a 2000 z71 FWIW.

 

Yeah, I did the 80E swap on my old truck too after blowing the 60E up for the second time. It was 2wd though, still had to add the second input for the 80E.

For whatever reason I could've swore I read about computer problems when swapping a 80E into a AWD vehicle. Maybe it's nothing more than reflashing to a 80E PCM file and hooking up the extra input like on any other 80E swap.

I'm not even doing the swap(right now anyway) and this is bugging the crap outta me.

 

Yeh i upgraded my 2k pcm to 2002 at the same time, so I just used a 2500hd pcm. Ofcourse I also did the 6.0 swap as well. So I didn't have to hack up the pcm, just swap as well.

I am not to sure about the extra input though. The AWD, at least mine, output sensor is on the tcase.